Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $118.53   11.565%   $132.238   $132.24   $132.25   $132.20  
  Purchase #2 $185.66   5.549%   $195.9623   $195.96   $195.95   $196.00  
  Purchase #3 $169.71   8.747%   $184.5545   $184.55   $184.55   $184.60  
  Purchase #4 $59.57   10.764%   $65.9821   $65.98   $66.00   $66.00  
  Purchase #5 $63.26   5.574%   $66.7861   $66.79   $66.80   $66.80  
  Purchase #6 $117.92   4.533%   $123.2653   $123.27   $123.25   $123.30  
  Purchase #7 $165.61   7.805%   $178.5359   $178.54   $178.55   $178.50  
  7 purchase totals = $880.26       $947.3242   $947.33   $947.35   $947.40